Telephone-transmitter



A. PLECHER.

TELEPHONE TRANSMITTER- APPLICATlON man APB. I9, 1912.

Patented Aug. 1, 1916.

2 SHEETS-SHEET I wmm ATTO R N EY wlmsssijd I A. PLECHER.

TELEPHONE TRANSMITTER.

APPLICATION FILED APR. I9. I9I2.

Patented Aug. 1, 1916.

2 SHEETS-SHEET 2.

ATTO R N EY ANDREW PLECI-IER, OF LAS ANIMAS, COLORADO.

TELEPHONE-TRANSMITTER.

Specification of Letters Patent.

Continuation of application Serial No. 633,461, filed June 16, 1911.This application filed April 19, 1912.

. Serial No. 691,892.

To all whom it may concern Be it known that 1, ANDREW PLECI-IER, acitizen of the United States, residing at Las Animas, in the county ofBent and State of Colorado, have invented a new and usefulTelephone-Transmitter, of which the following is a specification.

This invention has reference to improvements in telephone transmitters,and its ob ject is to produce a transmitter in which is combined theclearness and distinct transmission of a Blake transmitter with thevolume and wide range of the Hunnings transmitter with certainadvantages possessed by neither.

In accordance with one form of the present invention the speechreceiving diaphragm is not supported at the periphery after the commonpractice, but is free to vibrate at the periphery, being supported atthecentral portion, and in order that the diaphragm may respondvigorously to both the fundamentals of the tones of the human voice andalso to the overtones or harmonies, the diaphragm is multi-tuned, sothat different parts of it have different natu ral rates of vibrationcorresponding to the fundamentals and the overtones of speech and othersounds uttered against the dia phragm, wherefore the sound componentsare to a large extent individually strengthened as compared to sound orspeech transmission through diaphragms as ordinarily constructed. Themulti-tuning. of the diaphragm is advantageous when employed inconnection with other features of the invention, but improved resultsmay be obtained in speech or sound transmission when the diaphragm isnot especially tuned, nor need the diaphragm be supported centrally andfree peripherally, but the contrary may be true with good results. Whenthe diaphragm is multi-tuned it is customary to employ a metallicdiaphragm free tovibrate at the periphery and locally tuned about themarginal portion, while in the path of the peripheral portion of thediaphragm an electrical conducting medium is supported in a manner to beengaged by the diaphragm, the support being of a more or less elasticnature, but loose granules, such as are employed in connection with theHunnings transmitter, are avoided, and the conducting medium opposed tothe diaphragm. is customarily film-like either in the form of a metallicleaf, or in the form of fine powder,

or granules of metal or carbon caused to be strongly adherent to thecarrying surface, which latter, however, need not be conductmg.

In another and important form of the invention the use of a metallicdiaphragm is avoided, and in its place there is provided a membranewhich may be stretched until sufficiently taut for the purposes of theinvention, and this diaphragm membrane is provided on one face with aconducting film which may be quite thin, and yet, because of its largesurface, will provide ample c0nducting capacity for heavier currentsthan are possible with the usual granular or Hunnings form oftransmitter. Opposed to the conducting face of the membrance, which faceis remote from that against which speech is uttered, there is provided aconducting plate which may be polished and then cross-hatched orotherwise treated to provide a multitude of points which not onlyprevent sticking of the electrodes made up of the plate and conductingfilm, but provide many points from which electrical discharges mayreadily pass. Y

By adjusting the back plate, as it may b called, into proper relation tothe conducting surface of the membrane, no current will pass when theparts are at rest, but as soon as speech, which may be taken as typicalof any sound to be transmitted, is uttered against the diaphragm, thelatter is vibrated into and out of contact with. the back plate, thusestablishing make-and-break transmis- Patented na i, was. i

sion with the great variation in resistance of such a type of telephonictransmission, but while there is mechanical make-and-break in thecircuit, electric make-and-break is avoided, for the broad surface ofthe conducting film of the membrane and the broad surface of the backcontact at once establish condenser conditions, the discharges of whichmaintain the continuity of the circuit electrically, therebyestablishing in effect a variable contact transmitter wherein thevariations of resistance is far in excess of the best form of commercialtelephone transmitters, and the distant receiver is actuated withcommensurate vigor.

The invention will be best understood. from a consideration of thefollowing do i l l tailed description taken in connection with theaccompanying drawings forming a part of this specification, with theunderstanding that while in the drawings different embodiments of theinvention are disclosed, the invention is not confined to any strictconformity with the showing of the drawings, but may be embodied in anymanner which does not mark a material departure from the I salientfeatures of the invention.

In the drawings :Figure 1 is a more or less schematic representation, inmost .part in section, of a transmitter wherein the make-and-break andthe condenser effect is produced, but refinements "of construction areomitted. Fig. 2 is a face view of a back contact constructed inaccordance with the present invention and wherein the showing may beconsidered as more or less exaggerated. Fig. 3 is a longitudinal sectionthrough a transmitter head with the invention applied, wherein thediaphragm is of the conductive-film membrane type. Fig. 4 is a plan viewwith parts omitted of a transmitter of the multi-tuned diaphragm typewith one of the electrodes in the form of a conductive-film. Fig. 5 is asection on the line 5-5 of Fig. 4, with the supporting base omitted.

In the drawings two general types of transmitter are shown, in both ofwhich a conducting film is provided as one of the electrodes.

In Figs. 4 and 5 is disclosed the multituned metal diaphragm type, whilein Figs.

'1, 2 and 3 the disclosure is directed to the membranetype of diaphragmwherein the I circuit may be completely broken mechanically on themovement of the electrodes away one from the other, but wherein thecondenser efi'ect maintains the electrical continuity ofthe circuit.transmitter have parts in common, but as the forms-of Figs. 1, 2 and 3embody a greater departure from the ordinary telephone transmitter thanthe form of Figs. 4 and 5, the following description will be directedfirst to the forms of Figs. 1, 2 and 3.

Referring more particularly to Fig. 1, there is shown a support 1carrying a foot member 2 on which is erected a post 3 in turn supportinga ring 4 engaging about a bead 5 surrounding one end of a mouthpiece 6into which speech may be uttered, the word speech being .used forconvenience of description to mean not only vocal, but other sounds,although customarily telephones are used in a great majority, ofinstances for speech.

Clamped between the ring 4 and head 5 is amembrane 7 of any suitableflexiblematerial, of which rubber may be taken as an example, butwithout confining the invention to the use of rubber alone. One side ofthe membrane 7 has applied thereto a Both forms of the '11 is shown, andthese guides receive a foot 12 from which rises a post 13 terminating ina disk or plate 14 having a surface parallel with the film 8. The base 1carries a screw 15 passing through the post 13 whereby the latter may beadjusted toward and from the i post 3 to bring the plate 14 into thedesired relation with the film 8 of the diaphragm 7. Fast to the post 13is a binding post 16 to which the other lead 17 of the circuit may beconnected, and the circuit is customarily charged with a current of highamperage and low potential. That face of the plate 14 toward the film 8is scored or cross-hatched, or suitably formed so as to present amultitude of points or projections of minute area toward the film 8, notonly to prevent stick? ing between the film 8 and plate 14, but toprovid a multitude of discharge points.

In Fig. l'the distance between the film 8 when at rest and the plate 14is exaggerated, for in practice the distance is such that while when thediaphragm is at rest the circuit is broken between the film and plate,the vibratory movements of the diaphragm when toward the plate willcause contact between the film 8 and plate 14, thereby then establishingthe circuit to be immediately afterward broken by the return movement ofthe diaphragm.

In order that the diaphragm may respond in a lively manner to soundwaves, it is made more or less taut, so as to have a natural rate ofvibration determined by the character of the sounds to be transmitted,and as this rate of vibration may be brought about not only by thetautness of the diaphragm,

but by its thickness and character and otherconditions, no specialdirections can be given as to this matter, but the mounting of thediaphragm to produce the natural rate of vibration is a matter wellwithin the province of one well familiar with the principles ofacoustics.

While the structure of Fig. 1 when properly adjusted will operate forthe transmission of speech it lacks certain of the refinements of acommercial type, but will answer for an understanding of this part ofthe invention so far as the electrical actions are concerned.

Suppose that the instrument of Fig. 1 is l lt) connected up in atelephone circuit in the usual manner of connecting a telephonetransmitter, then when speech is uttered into the mouthpiece 6 thediaphragm 7 is set into vibration in accordance with the uttered sounds.The film 8 is moved against the plate 14 in one phase of its movementand out of contact and away from the plate 14 in the other phase of itsmovement, thus establishing make and break conditions, with theresultant great variation in resistance in the transmitter circuit withcorrespondingly great variations in the line and commensurate variationsat the distant receiver. As is well known such conditions will notresult in the intelligible transmission of speech. There are, however,two expanded conducting surfaces represented by the film 8 and plate It,which during the period of break are separated by a very thin air space,while the roughened surface of the plate 14 presented toward the film 8provides a multitude of fine points from which the current will flow.(in the break of contact condenser conditions are estab-- lished, sothat the electrical continuity of the "circuit is maintained byelectrostatic induction. The result of this action is that there isproduced upon the local circuit pulsating currents closely approachingin degree of variation currents produced by make-andbreak conditions,but still without any break in the circuit when considered electrically,while the sound produced at the receiver has all the characteristics ofthe original sound uttered against the transmitter and is reproducedwith greater intensity and more clearly and naturally than is the casewhen transmitters as ordinarily constructed are emplo ed.

While the structure shown in Fig. 1 is capable of practical operationcertain refinements of construction are advantageous for commercialtransmitters, and in Fig. 3 there is illustrated a structure Welladapted for commercial uses. 1

Mounted on a stem 19 through the intermediary of a pivot joint 20 is ahead 21, the stem 19 representing either the post of a desk set, or thearm of a wall set, or any other suitable support. The head 21,which maybe of metal, or which may be made of other material, is usuallyapproximately circular in outline, and is formed on one face with arecessv 22 of appropriate diameter communicating through an axialpassage 23 with another recess 24 in that face of the head 21 remotefrom the recess 22, and of smaller diameter.

The recess 22 is bounded by an annular rib 25 having an outer roundededge 26 and surrounding the rib 25 is an annular channel 27. Theperiphery of the head 21 exterior to the channel 27 is formed withscrew, threads 28 adapted to receive the inner threaded wall of a flange29 extending axially from one face of a cap 30 of a size to inclose therecess 22 and groove 27. The cap 30 is formed at the central portionwith a mouthpiece 31 of the usual flaring type common in telephoneinstruments, and whether or not the head 21 be formed of metal it iscustomary to construct the cap 30 of hard rubber or some similarmaterial.

The outer end of the recess 21 is covered by a membrane 32 of elasticrubber or other suitable material having that face toward the recess 22covered with a film 33 of some suitable conducting material of whichgoldleaf is to be preferred, since it is inert to atmospheric and otherlike influences, and is a good electric conducting material. Instead ofgold, silver or platinum may be used, or aluminum or graphite may beemployed, while operative results may be obtained from other conductingmaterials capable of carrying the desired current, though the conductorbe in the form of a film. The conducting film 33 is sutficientlyextensive to engage the rounded portion of the rib 25 so as to make goodelectric contact therewith, it being understood that this bead is madeof conducting material, whether or not the head 21 be so made, but forconvenience of description it will be assumed that the head 21 is ofmetal and the rib 25 is also made of metal. The margin of the membranediaphragm 32 is engaged between two clamping rings 34, 35 of anysuitable material, say metal, and these rings may be double walled, asindicated, so that the engaging portions may be made slightly elastic togrip the membrane, and one of the rings, say the ring 34, is formed witha channel 36 in which may be lodged anti-friction inner face of the cap30. When the parts are assembled, and after the margin of the membranediaphragm 32 is clamped between the rings 34 and 37 the latter areintroduced into the channel 27 and then the anti-friction balls 37 arelodged in the channel 36 which operates as a ball-race-way, and then thecap 30 is screwed on to the head engaging the balls 37 and forcingtherings 3% and 35 into the channel 27, thus stretching the membranediaphragm 32 over the rib 25 until the desired tension is established inthe diaphragm, whereby the latter may be tuned to any desired degree.

Extending through the passage 23 is a rod 38 surrounded by a sleeve 39of insulating material, since -the head 21 is made of metal. At one endthe rod 38 carries a disk 14 like the disk lat of the structure shown inFig. 1, and this disk 14 has the face remote from the rod 38cross-hatched to form a multitude of closely associated projections 40,although these projections may be otherwise formed than bycross-hatching, such cross-hatching being in the form of grooves atappropriate angles to cause-the projections. The grooves may be quitefine and the. projections quite minute, "so that the free face of thedisk 14 diameter has more or less the appearance of being roughened, butthe points of the projections should lie in as nearly one plane as maybe and this plane should be as nearly parallel with the plane of thefilm 33 as may be, and likewise the points or projections of the disk 14should be as close as practicable to the film 33 without actual contactwhen the parts are at rest.

All the parts are shown exaggerated both in size and position in Figs.1, 2 and 3, this being rendered. necessary by the limits of illustrationand the separation of the conducting face of the diaphragm and the faceof the disk contiguous to the diaphragm is greater in the showing of thedrawings than need be in practice, and the thickness of the film 33 andthe size of the projections 40 are exaggerated.

While in the drawings the head '21 is shown as of considerable diameter,it is customarily in practice to make it of about the of telephonetransmitters as usually employed in telephgne sets.

That end of the rod 38 remote from the disk 14 is threaded, as indicatedat 41, and extends into the recess 24. The threaded end 41 of the rod 38receives a nut 42 formed on a spring washer 43, which in turn bearsagainst another washer 44. which may be made of some insulatingmaterial, such. as

mica, and this washer 44 engages the inner wall of the recess, 25.Surrounding the sleeve 39 between the disk 14 and the inner Wall of therecess 22 is a spring 45 resting at the end remote from the disk 14against a disk 46 of mica or other suitable insulating material lodgedagainst the inner wall of the recess 22.

' 21 by screws 50 or in any other appropriate manner, the conductor 48being carried through a perforation 51 in the cap 49. The conductor 48is included in one side of the usual local transmitter circuit, whilethe other side of this circuit includes a conductor 52 secured to thehead 21 when this head is of metal or to the rib 25 when thehead is ofsome other material, the purpose being to include the film 33 in oneside of the circuit and the disk 14 in the other side thereof, so thatthe film and disk constitute the terminals of the local transmittercircuit.

When the parts are at rest the film 33 and roughened face of the disk 14are separated sound waves the film 33 is moved into contact with themany points 40, whereby on one phase of movement contact is made andincreased to a maximum, and on the other phase of movement this contactis broken, so that on this respect the transmitter is a make-and-breaktransmitter with a variable contact agreeable to the extent of vibrationof thediaphragm on the one phase of movement of the diaphragm. Onthebreak of the circuit the extended surfaces of the disk 14 and film 43separated by a minute air space become in effect a condenserestablishing electrostatic induction, so that there is no actual breakin the electrical conditions, the many fine points 40 contributing tothe flow of current across the air gap without, however, theestablishing of any minute arcs as often occur in the granular type ofmicrophonic transmitter when heavy current is passing and which giverise to the flying effect.

Practice has demonstrated that a much larger current may be employedwith the phragm 32 is established by turning the cap 30 to screw it onto or unscrew it from the head 21 to the requisite degree and therelation of the disk 14 to the conducting face of the diaphragm isreadily established by means of the nut 42, the ball bearings 37preventing any twisting of the rings 34 and 35 While the cap '30 isbeing turned to establish the desired adjustments.

Although the film 33 may be extremely thin it presents a large surfaceand extensive contact at the rib 25, while the diametric'extension ofthe disk 14 is also considerable, wherefore ample conducting capacity isprovided for the heavy current which may be' employed, and this currentas before statedmay exceed, without detrimental effect and withadvantage, the current which it is possible to employ with priorcommercial types of transmitters.

Some, though not all, of the features of the transmitters of Figs. 1, 2and 3 are retained in the transmitter of Figs. 4 and 5 where thecondenser effect is not realized and where great variation of contactmay be brought about by causing the make-andbreak in part only and notthroughout the sound responsive elements as occurs in Figs. 1 and 3.

Referring now more particularly to the structure shown in Figs. 4 and 5there is a base 53 on which is erected a post 54 terminating in anupstanding yoke 55 having at g the free ends of the legs of the yokebearings 56 for trunnions 57 on opposite sides of a hollow body 58, thishollow body being comparatively flat and rounded at the" edges with oneside 59 extended in the form of a neck terminating in an expandedmouthpiece 60, the said mouthpiece communicating with an interiorchamber 61 substantially coextensive with the body through the neck 59by way of the passages 62, while diametrically opposite the neck 59. apassage 63 is formed through the edge wall of the body 58. @ne fiat wallof the body 58 is in the form of a disk 64, the edge of which isthreaded to fit like threads in the body portion, so that the disk 6-1may be applied to or removed from the body at will, whereby access maybe had to thechamber 61 when desired.

The body 58 and mouthpiece as well as the removable member 64 may bemade of metal or may be made of some material of an electricallyinsulating character. When the body member is made of metal there issecured to the center portion of the cover member 64 a block 65 ofinsulating material extending entirely through the member 64, while theopposite wall of the body member 58 has a like block 66 lodged therein.

The interior chamber 61 is sufliciently extensive to receive a disk 67of insulating material, to the periphery .of which there is applied atube 68 of some material such as elastic rubber. and may be soconstructed as to present the characteristics of a pneumatic tire or theelasticity of the rubber alone may be depended upon for under somecircumstances a simple ring of rubber will give good results. Thisrubber ring or tube is covered with a film 69 of some conductingmaterial of whichgold leaf is to be preferred, although silver orplatinum will give good results and even aluminum or graphite may beemployed, but not with such advantage as gold. The diameter-of therubber tube or ring 68 is greater than the thickness of the disk 67, sothat the tube projects laterally beyond the plane of either face of thedisk 67. Carried centrally by the disk 67 and projecting axially fromopposite sides thereof are rods 70, 71, respectively, each secured tothe disk 67 by an adjusting nut 7 2 next to the disk, and another nut 73more distant from the disk, the nuts 7 2 and 7 3 clamping between them adiaphragm 7-1, there being such a diaphragm on each side of the -disk67, while the diameter of the diaphragm, which is of metal, is such thatits periphery engages the conducting film surface 69 of the tube or ring68 throughout its circumference, the marginal portions of the twodiaphragms being electrically connected when at rest by means of thefilm 69. The rods 70 and 71 are long enough to pass through therespective blocks 65 and 66, and exterior to these blocks the rods mayreceive This tube is an endless tubelook nuts and each terminates in abinding post 7 6 to receive respective conductors 77, 78 of the localtransmitter circuit.

When the structure is assembled, the rods 70 and 71 are secured to thedisk 67 in axial relation thereto and project from opposite sidesthereof. The tube or ring 68 properly coated with conducting material isthen sprung upon the disk where its elasticity will hold it in place,the periphery of the disk being shaped to receive and retain the rubberring. The nuts 7 2 are applied to the respective rods 7 0 and 71, andthen the diaphragms 74 are placed upon the rods and are locked in placeby the nuts 73. The cover member 64 having been previously removed, thediaphragm holder so far assembled is introduced into the chamber 61through the opening left by the removal of the cover member 64, suchopening being of sufiicient size for the purpose. The rod 71 is passedthrough the block 66 and then the lock nut 75 is applied, after whichthe binding screw of the corresponding binding post 76 is inserted andthe conductor 7 8 may be secured to the binding post either at this timeor later. The cover 64 may now be screwed into place, the passage in theblock 65 for the rod 70 being large enough for the purpose and then thecorresponding clamp 9 nut 75 may be applied, after which the conductor77 may be attached to the corresponding binding post 76, it beingunderstoodthat the diaphragms 74% have been properly adjusted before theassembling of 10 the completed structure. The only rigid support foreach diaphragm is at the center, while the peripheral portions of thesediaphragms are slit toward the central portion of the diaphragm to formtongues 79 having different natural rates of vibration, and while eachdiaphragm may have more than one tongue tuned to respond to the samerate of vibration, a sufficient number of tongues are provided topractically .cover the range of vibration of the fundamentals andovertones of a suflicient number of the sounds within the range ofthenormal human voice to cause vigorous selective response of portions ofthe diaphragm to such tones and overtones whereby the over tonesparticularly are not choked oi, as occurs with the ordinary peripherallyclamped diaphragm and the resultant. transmission closely approaches innaturalness and purity of tone the sounds uttered at the transmittingend of the system.

62 into the chamber 61 and finally emerge 13a at .the passage 63 withoutthe liability of rebound or reflection.

In the structure shown in Figs. 4 and 5 the movements of the tongues 7 9may be suflicient to cause a break of the circuit at together, and theymove simultaneously away from such conducting film, so that there isproduced a greater variation in resistance than occurs with the ordinarydiaphragm, and this variation of resistance is augmented by the moreviolent movements of the atuned tongues which respond with increasedamplitude to those sounds to which they are tuned. Moreover, thediaphragm being supported at the center only and free to vibrate at themargins is therefore more sensitive to the action of sound waves and.the vibrations are correspondingly more pronounced, wherefore theimpulses produced upon the line are more intense and the distantreceiver is more vigorously acted upon than is the case in telephonesystems as customarily installed.

In both forms of the transmitter shown in the drawings the contact is byway of a conductor filmwh'ether of metal or carbon in some form.Considering the membrane of Figs. 1 and 3, or the tube or ring of Figs.4 and 5 as being made of rubber or some such material, the film of goldor other metal may be applied by first covering the diaphragm or thetube with a suitable size and then applying a. metal either in the formof a thin foil or otherwise, or in the case of aluminum or graphite theconductive film may be produced by applying a substance mentioned in theform of a paint, or a solution of gun cotton may be applied to therubber or other like surface in a manner similar to .the production ofincandescent lamp films and the gun cotton surface may then be flashed.Experience has demonstrated,however, that the results obtained fromforms of carbon for the conducting film are not equal to those obtainedfrom metal, while goldleaf .appears to give the best results.

With the present transmitter packing is of course impossibleirrespective of the position of thetransmitter, since there .are noloose particles present as in the granular microphonic element.

Moreover, in both forms of the transmitter as included in. thisinvention theweight of the parts to be moved by the sound waves is smallas compared with the ordinary granular transmitter, wherefore the partsmove more vigorously and the overtones or harmonics are not blotted outeither actually or effectively.

With the transmitter of Fig. 3 the spring 45 may respond to the impactof the diaphragm, and in [the structure shown in Figs. 4 and 5 therubber ring or tube will yield slightly, so that in each case there is ayielding back contact. WVhile in the structure of Figs. 1 and 3 there isa mechanical break of contact, electrical continuity of the circuit ismaintained by electrostatic induction, and while in the structure ofFigs. 4

and 5 there may be actual mechanical break I of contact between some ofthe tongues and the conducting film, there are always some tongues inactual mechanical contact with the conducting film, wherefore theelectrical continuity of the circuit is maintained, but the variation ofcontact'may be very marked. Again, in the structure shown in Figs. 4 and5 the selective capacity of the tongues cause the impress upon thetransmission line of superposed polyphase currents customarilyrepresenting every component of the uttered sound, which in the vastmajority of cases is the human voice.

In both forms of the transmitter the diaphragm may be extremelysensitive to the sound waves, while the conducting surface ijs of suchlarge area that it is able to handle any desired amount of current whichmay be utilized to itsfull extent. Moreover, in the form of thetransmitter shown in Figs. 4: and -5 the contact though actual may beexceedingly loose when the diaphragms are at rest, thus contributing toa great range in the variation of contact even to the actual breaking ofthe circuit at some of the tongues.

In the structure shown in Fig. 3 the parts moving under the impulse ofthe sound waves may be highly sensitive to sound waves and may be tuned.This admits of the provision of an instrument of the makeand-breakelectrostatic-induction type of transmitter with a plurality ofdiaphragms each'difi'erently tuned from the others and all associated,in sound receiving relation to a single mouthpiece, so that the samereinforcement of the components of sounds may be obtained as is presentin the form of the invention shown in Figs. 4 and 5. It is feasible toprovide as many as twelve diaphragms in conjunction withasinglemouthpiece.

It is not necessary that the free face of the disk presented toward theconducting side of the membrane diaphragm in the structures shown inFigs. land 3 should be cross-hatched or checkered or otherwise roughenedin effect, but such formation of said free face prevents cohesion of thedisk and diaphragm and is, therefore, to be preferred. It is alsoadvisable that the free face of the disk be highly polished before beingroughened, checkered or cross-hatched.

The membrane diaphragm need not be more than simply taut for the naturalrate of vibration may be obtained by variations in thickness, diameter,tension or by the use of dampers. The checkering, cross-hatching orroughening of the plate or disk constituting the back electrode is notonly effective with respect to preventing cohesion, but increases theelectrostatic condition and striking distance of the current bypresenting many sharp points to the opposite or movable electrode orcont-act.

Again, when the potential in the local transmitter circuit isconsiderable, as, for instance, when the source of current comprisesquite a number of cells in series, the membrane is very slightly pulledtoward the back contact, whereby there is produced an electroscopicbalance condition, wherefore the action of the speech vibrations utteredagainst the diaphragm are correspondingly more effective because "of thecondition of unstable equilibrium established.

The transmitter of the present invention differentiates from priortransmitters by several distinctive characteristics, among which may benamed the mechanical or physical make andbreak without destroying theelectrical continuity of the circuit whereby great variation ofresistance is obtainable and at the same timesuch variation is gradualand not sudden as would occur where the mechanical or physical break ofthe circuit is accompanied by a like break in the electrical continuityof the circuit. The structure of the transmitter provides for anexceedingly great amplitude of vibration in a membranous diaphragm witha coextensive conducting film. The electrostatic pull on the diaphragmwhich exists causes a readiness for instantaneous action and return toinaction. The checkered or scored back electrode presents an enlargedsurface with 1. A telephone transmitter provided with two electrodes inface to face relation and electrodes movable into and out of contactunder the action of sound waves, one of said electrodes being in theform of a membrane covered, by a conductive film and the otherelectrode. being shaped to provide numerous points for contact with afilm, said contact points being in fixed relation one to the other. I

3. A telephone transmitter provided with electrodes, one of which is inthe form of a conductive film and the other of which is laterallyextended and formed with numerous points presented toward the film forcontact therewith, one of said electrodes being responsive to soundwaves to vibrate under the action thereof and having a range of movementsutficient in one direction to cause contact between the film and moreor less of the numerous contact points of the other electrode withvarying pressure depending upon the sound waves acting thereon, and alsohaving a range of movement in the other direction sufiicient to entirelyI of contact with the other and to contact during its vibration towardthe other to varying extents therewith.

5. In a telephone transmitter, a conducting film and a disk-shapedconducting memher in close proximity thereto, said members having theareas of their facing portions sufiiciently extensive to establish anelectrostatic relation between them, the conducting film having aresilient backing, and one of said members being related to the other tovibrate under the action of sound waves into and out of contact with theother and to contact during its vibration toward the other to varyingextents therewith.

6. In a telephone transmitter, a conducting member having a contactsurface divided into a plurality of contacting parts 111 fixed relationone to the other, and a vibratile conductive film in close proximity tothe conducting member and having a range of movement under the action ofsound waves to engage varying numbers of the contacting parts when movedtheretoward and wholly disengaged from the contacting parts when movedin the other direction,

7 A' telephone transmitter having electrodes in electrostatic inductiverelation and out of mechanical contact when at rest and related to makephysical electrical contact when vibrating under the action of the soundwaves to be transmitted.

8. A telephone transmitter having electrodes provided with extendedconducting surfaces in electrostatic inductive relation one to the otherand also located one with referenc'e'to the other to make physicalelectrical contact when vibrated under the action of sounds tobe'transmitted.

9. A telephone transmitter provided with a membrane diaphragm responsiveto sound waves uttered against it and provided on the surface remotefrom that receiving the sound waves with a conducting film, and a backelectrode in electrostatic inductive relation to the conducting film' onthe diaphragm and within the range of movement of the conducting filmunder the action of sound waves to cause physical electric con-. tactbetween the film and back contact.

10. A telephone transmitter provided with a membrane diaphragmresponsive to sound waves uttered against it and provided on the surfaceremote from that receiving the sound waves with a conducting film, and aback electrode in electrostatic inductive relation to the conductingfilm on the diaphragm and within the range of movement of the conductingfilm under the action of sound waves to cause varying physical electriccontact between the film and back contact, the back contact having thatface presented toward the conducting film provided with numerouscontact'points in fixed relation one to the other.

11. A telephone transmitter provided with a non-conductive membranediaphragm supported at the margin and provided on one face with aconducting film coextensive to the marginal support, and a back contactin operative relation to the conducting film and extended toward themarginal portion of the latter, said back contact having the facepresented toward the conducting film formed into a multitude of fixedpointed projections constituting contact points, the diaphragm having arange of movement under the impact of sound waves to cause it to engagevarying numbers of the projections when moved toward the back contactand to wholly disengage therefrom when moved away from the back contact.

13. A telephone transmitter provided with a membrane diaphragm having aconducting 80 film on one face, a back contact in operative relation tothe conducting film, a marginal support for the diaphragm, concentricradially elastic clamping rings for gripping the marginal portion of thediaphragm, said rings being of greater diameter than the marginalsupport for the diaphragm, and a cap member for the transmitter movableinto operative engagement with the clamping rings to force them axiallywith relation 90 to the diaphragm support to place the diaphragm underradial stress.

14. A telephone transmitter comprising a body member having a riboutstanding from one face with a channel exterior to and surroundingsaid rib, and said body member be- 'ing screw threaded exterior to thechannel, a cap member having a threaded flange adapted to the screwthreads of the body member and of a size to cover the rib and channel, amembrane diaphragm provided on one face with a conducting film and of adiameter to engage the rib and enter the channel exterior thereto,concentric clamp rings adapted to receive between them the .peripheralportion of the diaphragm and of a size to enter the channel outside therib, said rings being adapted to be engaged by the cap to stretch thediaphragm over the rib, and a back contact carried by the head inoperative relation to the film on the diaphragm.

15. A telephone transmitter comprising a body member having a riboutstanding from one face with a channel exterior to and sur- 1 roundingsaid rib and said body member being screw threaded exterior to thechannel, a

cap member having a threaded flange adapted to the screw threads on thebody member and of a size to cover the rib and channel, a membranediaphragm provided on one face with a conducting film and of a diameterto engage the rib and enter the channel exterior thereto, concentricclamp rings adapted to receive between them the peripheral portion ofthe diaphragm and of a size to enter the channel outside the rib, saidrings being adapted to be engaged by the cap to stretch the diaphragmover the rib, and a back contact Carried by the head in operabody memberhaving a rib outstanding from one face with a channel exterior to andsurrounding said rib, and sald body member being screw threaded exteriorto the channel, a cap member having a threaded flange adapted to thescrew threads on the body member and of a size to cover the rib andchannel, a membrane diaphragm provided on one face with a conductingfilm and of a diameter to engage the rib and enter the channel exteriorthereto, concentric clamp rings adapted to receive between them theperipheral portion of the diaphragm and of Ali a size to enter thechannel outside the rib, said rings being adapted to be engaged by thecap to stretch the diaphragm over the rib, and a back contact carried bythe head in operative relation to the film of the diaphragm, said backcontact having the face presented toward the film provided with numerouspoints, and said back contact having an adjustable mounting in the headfor determining its relation to the film of the diaphragm.

17. A telephone transmitter provided with a suitable head, a screw capadapted to the head and provided with a sound receiving mouthpiece, anda membrane diaphragm adapted to the head between the cap member and saidhead, the head member having a support for the marginal portion of thediaphragm, and holding means for the peripheral portion of the diaphragmoutside the support in' the path of the cap member for engagementthereby to readily tension the diaphragm, said peripheral holding meansfor the diaphragm being provided with antifriction devices between itand the cap. 7

18. A telephone transmitter having normally separated electrodesconstructed and associated to make variable contact under the action ofsound waves and to maintain the electrical continuity of the circuit,when out of mechanical contact by electrostatic induction.

19. A telephone transmitter having normally separated electrodesconstructed and associated to make variable contact under the action ofsound wavesand to maintain the electrical continuity. of the circuit,when out of mechanical contact, by electrostatic induction, one of theelectrodes having its active surface in the form of a conducting filmand the other electrode in the form of a plate with a multi-pointed facepresented toward the film.

20. A telephone transmitter having a vibratory sound responsiveelectrode and a back electrode constructed and arranged to cause a rangeof vibration of the sound responsive electrode, under the action ofsound waves, into contact with the back electrode and out of contacttherewith and in the latter case establish electrostatic inductiverelations between the electrodes.

21. An instrument of the character described coi'nprising opposedcondenser elements one of which is mounted for vibration into and out ofphysical or mechanical contact with the other, and said condenser elements being associated to constitute electrodes for an electric circuit.

22. An instrument of the character described comprising condenserelements one of which is in the form of a conducting film with avibratile membranous support, and the other in the form of a conductingplate having the surface scored or checkered to present many points infixed relation one to the other toward the conducting film of the otherelement, and said condenser elements being associated and the one withthe vibratile support having a range of vibration to cause it to contactwith the conducting plate, whereby the condenser elements constituteelectrodes for an electric circuit.

23. An instrument of the character described comprising opposedcondenser ele- "ments one of which is vibratile and movableinto and outof contact with the other and provided with an expanded conductingsurface and the other of which is in the form of a conducting platehaving a surface in operative relation to the conducting surface of theother element, which surface of the second named element is scored orcheckered to present many pointed portions toward the conducting surfaceof the first named element.

24. A telephone transmitter having a diaphragm tuned to respondsympathetically to the sounds to be transmitted, and a laterallyexpanded back contact in electrostatic relation to the diaphragm andlocated within engaging distance of the diaphragm on vibrations of thelatter under the action of sound waves in a direction toward the backcontact.

25. A telephone transmitter having a diaphragm tuned to respondsympathetically to the sounds to be transmitted, and a lat- Wit.

erally expanded back contact in electro- .or roughened to presentnumerous conducting points toward the other.

26. An instrument of the character described having laterally expandedelectrodes in opposed relation and normally separated as my own, I havehereto af'fixed my sigby an a1r space, sald electrodes belng ofconnature 1n the presence of two \vltnesses. ductlng matenal and one ofthe electrodes being vibratile and in closerelation to the ANDREWPLECHER' 5 other to cause the electrodes when charged Witnesses: I

to be in a state of electro-static balance. F. W. LORING,

In testimony, that I claim the foregoing M. Frrswonrn.

